The significant association might require a larger study. When considering all the data together, the presence of anti-HBs produced by a natural HBV infection or by vaccination might be inversely associated with atopy in young adults. considered statistically significant. RESULTS This study population included 105 young adults aged less than or equal to 40 years old and 253 older adults aged greater than 40 years old. Two-hundred forty-five (68.4%) subjects had anti-HBs and 113 subjects (31.6%) had no antibody. One-hundred sixty-two subjects (45.3%) had the history of HBV vaccination; 124 (76.5%) subjects had the antibody and 38 subjects (23.5%) had no antibody. Antibody to hepatitis C virus and parasite eggs were detected in 4 (1.1%) and 15 (4.2%) subjects, respectively. The parasites included was significantly lower in the positive anti-HBs group than in the negative anti-HBs group (27 [11.0%] versus 22 [19.5%], was significantly lower in the positive anti-HBs group than in the negative anti-HBs group ((0.20 [0.06-0.65], was significantly lower in the positive anti-HBs group than in the negative anti-HBs group (13 [10.5%] versus 10 [26.3%], was significantly lower for the positive anti-HBs group than for the negative anti-HBs group (2 [5.0%] versus 4 [33.3%], em p /em =0.01). There were no differences in the prevalence rates for the sensitization to dog, the mould mixture, the tree mixture and mugwort between the two groups ( em p /em 0.05, respectively). DISCUSSION In the present study, we showed the negative association between the presence of anti-HBs and atopy or the sensitivity to D. farinae, which is known to be the most common allergen in this country in young adults, although this inverse association was not maintained in the older adults. To the best of our knowledge, this is the first study to show that the presence of anti-HBs produced by a natural HBV infection or vaccination may be inversely associated with atopy. This finding might partly explain why atopic disorders are least prevalent in Asia and Africa2), where the prevalence of HBV infection has been higher, and in some countries where the HBV vaccine has been introduced into their national immunization programmes13). It is known that the immune Topiroxostat (FYX 051) response to HBV is E2A responsible both for viral clearance and for the pathogenesis of the disease during HBV infection9). During the natural course of chronic HBV infection, some patients undergo a spontaneous exacerbation of the liver damage with an elevation of serum aminotransferases, and this may result in seroconversion of the hepatitis B e antigen (HBeAg) to the antibody to HBeAg (anti-HBe), and it also results in viral clearance. These hepatitis flare-ups are associated with the enhancement of the virus-specific T helper cell reactivity17-19). Rossol et al.12) have recently shown that a substantial increase in IL-12 production, along with the induction of Th1 cytokines such as IFN- and IL-2, is required for the sustained immune control over HBV replication, and this is manifested by seroconversion to anti-HBe. In the transgenic mouse models, it has been demonstrated that IL-12 can suppress HBV-replication by Topiroxostat (FYX 051) the induction of IFN-10, 11). The HBeAg begin to fall at the onset Topiroxostat (FYX 051) of illness and it may be undetectable at the time of the peak clinical illness. HBsAg becomes undetectable and anti-HBs arise during recovery, several weeks to months after the loss of HBeAg. Anti-HBs is a long-lasting antibody and it is associated with immunity15). Accordingly, it might be considered.